So I've been analyzing the tiles, referencing Hidden Paths and Secret Passages, using the Karim Redesign (the only version I've got of this game). Been trying to determine the distinguishing factor between the two, and noticed in Karim's tiles and on the Record of Fate (aka Personal History Sheet), the Borderlands has a Secret Passage, the Cavern has Secret Passages, yet the Caves has Hidden Paths. I was confused from a thematic standpoint. Why weren't all underground tunnels secret passages? So I decided to check the original games Personal History Pad and tiles for reference to be sure.
As it turns out, there's a discrepancy between the two versions. I checked the third edition rules for some clarification, and here's what it says about roads in general:
2.1 THE MAP
2.1.1c.: The clearings are connected by four kinds of roadways: black underground "tunnels", light brown "open roads", dark brown "hidden paths" and grey-speckled black "secret passages".
Ahah. So apparently all underground tunnels that are supposed to be hidden/secret should only be secret passages.
Caves: Green: HP 2-3; Enchanted: HP 1-6
Caves: Green: SP 2-3; Enchanted: SP 1-6
Thankfully this only seems to be an issue on the Record of Fate, which is easily remedied. The artwork on the Caves and it's Secret Passages follow the same style as that on the Caverns and Borderlands. But it does make me wonder, how big of a difference does this actually make? Are there any abilities or treasures that only affect Hidden Path rolls/discoveries but not Secret Passage rolls/discoveries? The main difference I can tell is that it's possible to accidentally discover a chit when you're trying to discover a passage, or vice-versa, which is important considering how important it is to discover chits. So in that regard, the difference may seem small, but it's a significant difference if it becomes possible to do Locate rolls with the intention of finding secret passages and site chits in the same clearing. Useful too, considering how limiting caves can be for most characters.
Thematically, I'd imagine it as Passages are covering in shadows/darkness due to lack of light, whether from the roof of a cave, or the shape of a mountain pass. Making it so dark to see, you might accidentally stumble upon something else. While as hidden paths tend to be hidden in another way, by bushes and shrubs and other foliage.
My princess is not in another castle.
You can Peer adjacent tiles from any mountain clearing.
The Witch's familiar can only Peer.
The Magic Telescope is Peer only.
The Crystal Ball lets you Peer or Spell any hex.
The Talk to Wise Bird spell is Peer only.
Peering helps to Find Hidden Enemies in competitive games, either for spying or attacking.
I imagine Locating as physically poking and prodding to find something while Peering is just staring intently. Locating will help you find those treasure sites and secret passages because you're tapping on the walls and moving rocks around. Peering will help you notice the tracks of hidden enemies, a bunch of bootprints leading into the bushes, or "it sure is dank and patterful over in the caves to the south of this cliff".
Of course, if you roll a 1 then you have the choice from either table so you can still find a secret passage by peering or hidden enemies by locating but not likely.